Refrigeration



July 21, 1942.

R. M. BUFFINGTON REFRIGERATION Filed Dec. 12, 1938 2 Sheets-Sheet l ATTORNEY.

y 21, 1942- R. M. BUFFINGTON 2,290,532

REFR I GERAT ION Filed Dec. 12, 1938 2 Sheets-Sheet 2 1N VENTOR.

ATTORNEY.

vent.

Patented July 21, 1942 REFRIGERATION Ralph M. Buiflngton, Evansville, Ind., assignor to Servel, Inc., New York, N. Y., a corporation of Delaware Application December 12, 1938, Serial No. 245,098

11 Claims.

My invention relates to refrigeration and it is an object of the invention to extend the field of usefulness of carbon dioxide as a refrigerant fluid.

I utilize carbon dioxide as a refrigerant by reducing the vapor pressure of the pure liquid fluid by dissolving it in a suitable solvent, evaporating the fluid from solution to produce refrigeration, and condensing the fluid by absorption in the sol- The invention will be more fully understood upon reference to the following description in connection with the accompanying drawings in which Fig. 1 shows more or less diagrammatically a compression type refrigeration system embodying the invention; Fig. 2 shows more or less diagrammatically a two-pressure absorption type refrigeration system embodying the invention; and Fig. 3 shows more or less diagrammatically a uniform pressure type absorption refrigeration system embodying the invention.

Referring to Fig. 1, an evaporator I isshown as a finned pipe coil. The upper end of evaporator I0 is connected to an expansion valve H. The lower end of evaporator I0 is connected to the upper part of a vessel l2. The upper part of vessel I2 is connected by a conduit l3 to the suction inlet of a motor driven compressor M. A condenser I5 is shown as a finned pipe coil. The upper end ofcondenser I5 is connected by a conduit Hi to the discharge side of compressor It. The lower end of condenser is connected by a conduit H, the inner passage [8 of a liquid heat exchanger l9 and a conduit to the expansion valve H. The upper end of condenser [E is also connected by a conduit 2!, the outer passage 22 of liquid heat exchanger I9, a conduit 23, a liquid pump 23, and a conduit 25 to the lower part of vessel l2.

The above described apparatus is evacuated and charged with a refrigerant fluid and a liquid absorbent therefor. Because it plays a part in normal body processes carbon dioxide is a relatively safe fluid for use in refrigeration, particularly in connection with air conditioning for comfort. I therefore use carbon dioxide as the refrigerant fluid in this system. Carbon dioxide has a high vapor pressure and its critical temperature is low (87.8" F.) To lower the pressure,

rosive liquid; that it is preferably non-volatile under the conditions of operation; and that the carbon dioxide is highly soluble therein. Examples of suitable absorbents in this class are mono-. di-, and tri-ethanolamine; mixtures of these with water; and diamino isopropanol. All of these absorbents are'both amines and alcohols, being later herein referred to as amino-alcohols, and

have the typical properties of such compounds.

They are low freezing, high boiling, alkaline compounds, and are soluble in water, alcohol, and other polar solvents. They are strongly enough alkaline to absorb carbon dioxide, and not too stronglyalkaline to permit easy regeneration of the carbon dioxide. In the above system, I therefore use, for example, diamino isopropanol as say, to one-half or one-third, and to carry out condensation of the carbon dioxide, I provide one of a class of solvents for carbon dioxide. A solvent in this class must be such that the carbon dioxide may be expelled from solution therewith by a moderate increase in temperature; that no solid phase be precipitated at any point in the cycle of operation; that it be a stable, non-corsolvent.

In operation of the system, the compressor M3 withdraws carbon dioxide gas from the evaporator vessel i2 through conduit IS. The pump 26 withdraws liquid from vessel I2 through conduit 25. The pump causes the withdrawn liquid to flow through conduit 23, liquid heat exchanger is and conduit 2i into the condenser it. The compressor it compresses the withdrawn carbon dioxide and discharges the compressed gas through conduit it into condenser 15. The compressed carbon dioxide dissolves in the liquid in condenser l5 and may therefore be liquefied at a temperature above the critical temperature of carbon dioxide. The resulting strong solution of carbon dioxide in diamino-isopropanol flows from the condenser it through conduit l'i, liquid heat ex changer I9, conduit 20, and expansion valve it into evaporator 80. The carbon dioxide evapo rates from solution in the evaporator l0 and is withdrawn through vessel l2 and conduit it by the compressor. The resulting weak solution accumulates in vessel l2 from which it is withdrawn by the pump 24 through conduit 25.

In Fig. 2 there is shown more or less diagrammatically a two pressure absorption type refrigeration system embodying the invention. There are parts of this system which are identical with that described in connection with Fig. 1 and like parts in Figs. 1 and 2 are indicated by the same reference numerals. In Fig. 2 there is, in place of a compressor, a liquid circuit including a generator 21, an absorber 28, a liquid heat exchanger 29, a liquid pump 30, and a float valve 3|. The generator 21 is heated by a burner 32 arranged so that the flame is projected into a flue 33 which extends upward through the generator.' Within the generator 21 are a series of bubble trays 34 so that vapor rising in the generator bubbles through descending liquid in the trays. The upper part of generator 21 is connected by a conduit 35 to the upper end of condenser |5. Conduit 35 is provided with a finned section 36 which serves as a rectifier.

The upper end of absorber 28 is connected to float valve 3|. The upper end of absorber 28 is also connected by a conduit 31 to the upper part of evaporator vessel |2. The lower end of absorber 28 is connected to pump 30. The discharge side of pump 30 is connected by a conduit 38, inner passage of liquid heat exchanger 29, and conduit 39 to the upper part of generator 21. a conduit 40, outer passage of liquid heat exchanger 29, and conduit 4| to the float valve 3|.

This system is also charged with carbon dioxide and diamino-isopropanol. In operation of the system, burner 32 heats generator 21; pump 24 pumps weak solution from evaporator l2 through liquid heat exchanger l9 into condenser l5, as described in connection with Fig. 1; and pump 30 pumps strong solution from absorber 28 through conduit 38, liquid heat exchanger 29, and conduit 39 into the upper part of generator 21. Strong solution flows downward in generator 21 over the trays 34 to the bottom of the generator from where it flows through conduit 48, liquid heat exchanger 29, and conduit 4| to the float valve 3|. In the generator 21 carbon dioxide is expelled from solution and flows through conduit 35 to condenser I5.

Carbon dioxide is dissolved in condenser l and the solution flows through conduit l1, liquid heat exchanger l9, conduit 20, and expansion valve into evaporator l8. Carbon dioxide evaporates from solution in evaporator I8, producing a refrigerating effect. Carbon dioxide flows from the evaporator vessel I2 through conduit 31 to absorber 28. Float valve 3| admits weak solution into the upper end of absorber 28. Carbon dioxide is absorbed into the weaker solution in absorber 28, and the resulting enriched solution is returned to the generator by pump 36 as previously described.

Referring to Fig. 3, there is shown an absorption type refrigeration system containing a pressure equalizing inert auxiliary fluid, such as hydrogen, and utilizing carbon dioxide as refrigerant and diamino isopropanol as absorbent. A generator 44 is heated by a burner 45, arranged so that the flame projects into a heating flue 46. The flue extends through chambers 41 and 48. The lower end of a standpipe 49 is connected to chamber 41. A vapor liquid lift conduit 50 extends from within chamber 48 upward to the upper part of standpipe 49.

An analyzer 5| has a lower chamber 52 and an upper chamber 53. There is a drain conduit 54 from the upper chamber to the lower chamber, and a small vapor lift conduit 55 from the lower chamber 52 to upper chamber 53. For further description of this type of analyzer reference may be had to application Serial No. 11,989 of Harry K. Bergholm, filed April 1, 1936, Patent No. 2,169,214.

An absorber 56 comprises a. finned pipe coil and a vessel 51 connected to the lower end of the pipe coil. The lower part of vessel 51 is connected by a conduit 58', outer passage of a liq,-

uid heat exchanger 59, and a conduit 68 to the.

analyzer chamber 52. Chamber 52 is connected by a conduit 6| to generator chamber 48. The upper part of chamber 52 is connected by a con- The bottom of generator 21 is connected by 49. Generator chamber 41 is connected by a conduit 63, inner passage of liquid heat can changer 59, and conduit 64 to the upper end of absorber 56. Conduit 64 is provided with a finned loop for air cooling.

An evaporator 65 is shown as a pipe coil located in a refrigerator storage compartment 66. The upper end of evaporator 65 is connected by a conduit 61, inner passage of a gas heat exchanger 68. and a conduit 69 to the upper part of absorber vessel 51. The lower end of evaporator 65 is connected by a conduit 10, outer passage of gas heat exchanger 68 and a conduit 1| to the upper end of absorber 56. The upper end of analyzer 5| is connected by a conduit 12 to the upper end of a condenser 13 shown as a finned pipe coil. The lower end of condenser 13 is connected by a conduit 14, outer passage of a heat exchanger 15, and a conduit 16 to the upper end of evaporator 65. The lower end of condenser 13 is also connected by an upward looped conduit 11 to the upper end of conduit 61.

The lower end of evaporator 65 is connected by conduit 16, a conduit 18, inner passage of heat exchanger 15, a conduit 19 and a conduit 80 to the upper end of condenser 13. Conduit 80 is a relatively small conduit to act as a vapor liquid lift. The lower end of conduit 80 is arranged in thermal exchange relation with analyzer 5| and the upward extending part of conduit 88 is arranged in thermal exchange relation with conduit 12. 80 is connected to conduit 19 and together these conduits form a downward loop.

Heat is applied to the generator 44 by burner 45 and carbon dioxide is expelled from solution in both chambers 41 and 48. Gas in chamber 46 causes liquid to rise in known manner through conduit 58 into the upper part of standpipe 49. Absorption liquid flows downward in standpipe 49 into chamber 41 and flows through conduit 63, heat exchanger 59, and conduit 64 into the upper end of evaporator 56. Liquid flows downward through evaporator 56 into vessel 51' and thence flows through conduit 58, liquid heatexchanger 59, conduit 68, analyzer 5|, and conduit 6| to generator chamber 48. Gas flows from the upper end of standpipe 49 through conduit 62, analyzer 5| and'conduit 12 to condenser 13. Liquid also enters the upper end of condenser 13 through conduit 80. The carbon dioxide is condensed into solution in liquid in the condenser and flows from the lower end of the condenser through conduit 14, liquid heat exchanger 15, and conduit 16 into the upper end of the evaporator 65.

Carbon dioxide evaporates from solution in evaporator 65. The gas flows from the upper end ofthe evaporator through conduit 61, gas heat exchanger 68 and conduit 69 to the absorber 56. The weakened absorption liquid flows from the lower end of the evaporator through conduit 18, heat exchanger 15, conduit 19, and conduit 88 back to the condenser. The upward flow of liquid in conduit 80 is caused by thermosyphonic or vapor lift action. Liquid is heated in conduit 80 by heat transfer from generator gas in analyzer 5| and conduit 12, causing expulsion of gas out of solution. The gas lightens the column of liquid in conduit 80 so that liquid rises to the upper end of conduit 88 and overflows into the condenser.

In the absorber 56, carbon dioxide is absorbed in the descending stream of liquid. The resulting duit 62 to the upper end of generator standpipe weak gas flows from the upper end of the ab- The lower end of conduit sorber through conduit ll, gas heat exchanger 68, and conduit back' to the evaporator.

What is claimed is:

1. A method of'refrigeration which includes condensing and evaporating carbon dioxide in the presence of diamino isopropanol.

2. A method of refrigeration which includes condensation and evaporation of carbon dioxide in the presence of a compound of the group consisting of primary, secondary and tertiary ethanolamines.

3. A' method of refrigeration which includes condensation and evaporation of carbon dioxide in the presence of a solvent therefor which is an amino-alcohol.

4. A method of refrigeration which includes evaporation of carbon dioxide from solution in an amino-alcohol, absorptionof carbon dioxide into solution in said absorbent, expulsion of the absorbed carbon dioxide from solution, and reabsorption of expelled carbon dioxide.

5. A method of refrigeration which includes evaporating carbon dioxide from solution in an amino-alcohol, withdrawing the evaporated carbon dioxide, condensing the withdrawn carbon dioxide by dissolving in said'solvent, and again v evaporating the dissolved carbon dioxide.

and means for withdrawing carbon dioxide gas from said evaporator.

'7. A refrigeration system as set forth in claim 6 in which said means for supplying carbon dioxide to said condenser is a generator, and said means for withdrawing carbon dioxide from said evaporator is an absorber.

8. A refrigeration system including a condenser, an evaporator, conduits connecting said condenser and evaporator forming therewith a circuit for circulation of a liquid amino-alcohol therethrough and therebetween, means for supplying carbon dioxide to said condenser, means for withdrawing carbon dioxide from said evaporator, and means operable by waste heat from the system for causing circulation of liquid in said circuit by gas lift action.

9. A method of refrigeration which includes supplying gaseous carbon dioxide under pressure, condensing said gaseous carbon dioxide in the presence of an amino-alcohol, reducing the pressure of the carbon dioxide and amino-alcohol, evaporating the carbon dioxide at the reduced pressure, separating the evaporated carbon dioxide from the amino-alcohol, increasing the pressure of the carbon dioxide, and again supplying the carbon dioxide under pressure.

l0. A method of refrigeration which includes heating a solution of carbon dioxide dissolved in an absorption liquid to produce gaseous carbon dioxide under pressure, condensing said gaseous carbon dioxide in the presence of an aminoalcohol, reducing the pressure of the carbon dioxide and amino-alcohol, evaporating the carbon dioxide at the reduced pressure, separating the evaporated carbon dioxide from the aminoalcohol, absorbing the carbon dioxide in the absorption liquid, increasing the pressure of the solution of carbon dioxide in absorption liquid, and again heating said solution.

11. A method of refrigeration which includes heating a solution of carbon dioxide dissolved in an absorption liquid to produce gaseous carbon dioxide under pressure, condensing said gaseous carbon dioxide in the presence of an aminoalcohol, reducing the partial pressure of carbon dioxide by mixture with an inert gas, evaporating the carbon dioxide at the reduced partial pressure, separating the gaseous mixture of carbon dioxide and inert gas from the amino-alcohol, ab- 

